Previously, there is known a fuel pump module that is installed in an inside of a fuel tank. This type of fuel pump module includes: a flange, which forms a lid to be installed to an opening of the fuel tank: a base, which supports a fuel pump; and a coupler, which rotatably supports the base. The fuel pump module is inserted into the fuel tank while rotating the base relative to the coupler.
For example, in the fuel pump module disclosed in JP2016-89739A (corresponding to US2017/0248106A1), a base main body of a base and a coupler are coupled together by using a coupling shaft portion, a connection hole (serving as a complex hole) and a stopper piece. The coupling shaft portion includes: a shaft part (serving as a small diameter part), which extends from a base part of the coupling shaft portion; and a bulging portion (serving as a large diameter part), which is formed at a distal end of the shaft part. The connection hole includes an engaging hole section and an insertion hole section, which are continuously formed together. Although the shaft part can pass the engaging hole section, the bulging portion cannot pass the engaging hole section. Furthermore, the bulging portion can pass the insertion hole section. The stopper piece can limit a movable range of the shaft part, which is placed in a state where the shaft part is received in the engaging hole section, toward the insertion hole section.
According to the technique recited in JP2016-89739A, the stopper piece is resiliently deformable. At the time of coupling the base main body to the coupler, the stopper piece is bent in a plate thickness direction of the stopper piece, so that the bulging portion can pass through the insertion hole section. Here, in a case of integrally molding the stopper piece with resin, it is necessary to provide a gap having a width equal to or larger than a predetermined value on both sides of the stopper piece due to restrictions on a strength of a mold die.
At the time of inserting the fuel pump module into the fuel tank, when the shaft part, which is received in the engaging hole section, is displaced toward the insertion hole section and contacts a side surface of the stopper piece, the stopper piece receives a load from the shaft part in an opposite direction that is opposite from the shaft part. In a case where a relatively large load or a relatively large torsion load is applied at the time of inserting the fuel pump module into the fuel tank, the stopper piece, which has relatively low rigidity, may be largely deformed in the opposite direction, which is opposite from the shaft part. In such a case, the shaft part may be displaced from the engaging hole section to the insertion hole section side. Once the shaft part is displaced from the engaging hole section into the insertion hole section, the shaft part may possibly be caught (i.e., arrested) by an inner wall of the connection hole and thereby may not be returned into the engaging hole section even after removal of the applied load. This may result in failure of relative rotation between the base main body and the coupler, and thereby the fuel pump module may not be placed in the appropriate orientation at the inner bottom surface of the fuel tank.